Technical Abstract:
Human norovirus (NoV) accounts for more than 90% of nonbacterial gastroenteritis. To date, the efficacy of human NoV inactivation interventions cannot be accurately evaluated because the virus is nonculturable. In this study, we aimed to estimate inactivation of human NoV by high pressure processing (HPP). We previously found that the primary mechanism of virus inactivation of cultivable murine NoV by HPP was disruption of the viral capsid structure, but not degradation of viral genomic RNA. Subsequently, stability of human NoV to HPP was estimated by targeting the virus capsid using human NoV virus-like particles (VLPs), structurally similar to native virions. The structure and receptor binding ability of human NoV VLPs were disrupted at 700, 800, and 900 MPa for 30, 10, and 2 min, respectively. Two methods were used to determine whether a human NoV GII.4 strain behaved similarly to human NoV VLPs, in response to HPP. First, the pressurized GII.4 strain was treated by RNase, prior to RNA extraction and real time RT-PCR. Results indicated that 600 MPa for 5 min inactivated human NoV. Next, the binding ability of pressurized virus particles to porcine gastric mucin (a HBGA like molecule)-conjugated magnetic beads (PGM-MBs) was used to determine whether capsid integrity and receptor binding ability of GII.4 remained intact following pressure treatment. It was found that 600-MPa for 5 min reduced binding of the virus to PGM-MBs by approximately 5 log, as determined by real time RT-PCR. Collectively, these results indicate that (i) human NoV VLPs may be more resistant to HPP than the native virion; and (ii) HPP is capable of inactivating a human NoV GII.4 strain under the optimized pressure parameters.